1. Field of the Invention
The present invention relates to a film deposition method.
2. Description of the Related Art
In response to high integration of a semiconductor memory, a capacitor using a high dielectric material such as metallic oxide as a dielectric layer has been widely used. Electrodes of such a capacitor are made of titanium nitride (TiN), for example, with a relatively large work function.
The TiN electrode is formed by depositing a TiN film on a high dielectric film by chemical vapor deposition (CVD) using titanium chloride (TiCl4) and ammonia (NH3) as source gasses, for example, and patterning the TiN film as disclosed in Japanese Patent No. 4583764, for example.
On the other hand, a method of depositing a film using an ALD (Atomic Layer Deposition) method or an MLD (Molecular Layer Deposition) method is known in which the film deposition is performed by depositing an atomic layer or a molecular layer. For example, as disclosed in International Publication No. WO2007/058120, a method of depositing a film for improving step coatability and adhesion of a film is known in which an initial film deposition is performed by using the ALD method and then a main film deposition is performed by using the CVD method. In the initial film deposition step, the ALD method is performed by introducing a Ru source gas into a process chamber so as to adsorb on a substrate while supplying H2 or NH3 into the process chamber as a first reaction gas. Next, in the main film deposition step, the CVD method is performed by introducing a Ti source gas into the process chamber so as to adsorb on the substrate while supplying O2 gas as a second gas.
However, in these days, there is a process that needs a very thin continuous TiN film having, for example, a thickness of 7 nm or thinner, in addition to forming such a TiN electrode. The TiN continuous film is grown by discretely forming TiN island films on a substrate at first, and then by gradually connecting the TiN island films to each other in this order.
Hence, in the event that a too thin TiN film having, for example, a thickness of 4 nm or thinner is assumed to be formed, the TiN island films are unlikely to be connected to each other so as to sufficiently form the continuous film, thereby forming a pinhole therein. Furthermore, in such a growth process as the island films gradually connect to each other, in an actual film deposition process, a film is not deposited on the substrate for a while from the start of film deposition, but only the film islands are formed. The actual film deposition starts after the elapse of a certain amount of time, which causes deposition lag time, thereby reducing a throughput.